KR20130031213A - Paste and method for connecting electronic component to substrate - Google Patents

Abstract

PURPOSE: A paste is provided to form a coupling between an electronic component and substrate with high reliability at a high temperature. CONSTITUTION: A paste contains a metal particle; one or more activators with two or more carboxylic acid units; and a dispersion medium. A method for connecting an electronic device to a substrate through a contact region comprises a step of providing a substrate with a first contact region and an electronic component with a second contact region; a step of providing the paste; a step of generating a structure where the first contact region and the second contact region are contacted to each other through the paste; and a step of sintering the paste and manufacturing a module which comprises the substrate and the electronic component connected to each other through the sintered paste.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a paste and a method for connecting an electronic device to a substrate,

The present invention relates to a paste for connecting an electronic device to a substrate and a method for connecting the electronic device to a substrate.

In the field of power electronics, securing electronic devices on a substrate is a challenging challenge.

The mechanical stress that occurs during operation of the terminal device requires that the connection between the electronic device and the substrate be maintained at a sufficient strength so that the electronic device is not detached from the substrate. Thus, it is common to use lead-containing solder paste, which has shown high reliability in terms of strength in connection technology in soldering processes connecting the layers. However, due to the toxicity of lead and its associated health hazards, a suitable alternative to the lead-containing solder paste has been sought. As an alternative to lead solder, it is currently being discussed that lead-free solder paste is well suited for forming a connection layer with high strength between the electronic component and the substrate. However, the solder has a low melting point which is not higher than the temperature at which the electronic device is exposed in operation. As a result, the reliability of the strength of the connecting layer during operation of the electronic device is greatly reduced.

High reliability in connection strength between the electronic component and the substrate can be achieved by a number of joining agents and connection methods. However, they often require high process temperatures and high process pressures, which cause damage to the connected components and result in high scrap rates in high volume production.

This is a fundamental reason for lowering the process temperature and the process pressure necessary for the connection method. In some applications, an adhesive is used to connect the parts. Through the use of adhesives, in some cases a high strength connection layer connecting the electronic component and the substrate can be obtained. However, there is a disadvantage of the adhesive technology in that the contact sites formed between the electronic element and the substrate are often insufficient in terms of thermal conductivity and electrical conductivity.

In order to meet the requirements relating to reliability, thermal conductivity, and electrical conductivity of connection sites, it has been known for some time that electronic devices and substrates are connected by sintering (see, for example, DE 10 2007 046 901 A1). Sintering technology is a very simple way to connect devices in a stable way. Using this sintering method, the connection is generally very successful if each of them includes a noble metal-containing contact area in connecting the electronic component to the substrate. However, it is often necessary to connect the electronic component and the substrate through one or more non-noble metal contact regions. Conventional sintering methods often fail to form stable connections through the non-noble metal contact regions.

Also, in the beginning, the use of a paste mainly composed of nanoparticles having a particle diameter of 100 nm or less has been proposed for connecting an electronic device and a substrate. However, the handling of nanoparticles involves health risks and is often avoided due to safety reasons.

It is therefore an object of the present invention to provide a paste connecting one or more electronic elements to one or more substrates through a contact region, wherein at least one of the contact regions contains a non-noble metal. Preferably, the paste is used to form a connection between the electronic device and the substrate to ensure high reliability at the temperature at which the electronic device is exposed during operation. The paste also preferably tries to overcome other disadvantages known in the prior art.

It is also an object of the present invention to provide a method of connecting one or more electronic devices to one or more substrates through a contact region, wherein at least one of the contact regions contains a non-precious metal.

These objectives are met by the subject matters of the independent claim.

Accordingly, the present invention provides a paste containing (a) metal particles, (b) at least one activator having at least two carboxylic acid units in the molecule, and (c) a dispersion medium.

The present invention also provides a method of connecting one or more electronic devices to one or more substrates through a contact region, wherein at least one of the contact regions contains a non-

(i) providing an electronic device having a substrate having a first contact region and a second contact region, wherein at least one of the contact regions contains a non-noble metal;

(ii) (a) a metal particle;

(b) at least one activator having at least two carboxylic acid units in the molecule; And

(c) a dispersing medium;

≪ / RTI >

(iii) creating a structure through which the first contact area of the substrate contacts the second contact area of the electronic device through the paste; And

(iv) fabricating a module comprising at least a substrate and an electronic component interconnected through a sintered paste by sintering the structure.

The present invention is based on the surprising discovery that the connection of an electronic element and a substrate through one or more contact regions comprising a noble metal, which has not been possible so far, can be achieved through sintering of a paste containing an active agent having two or more carboxylic acid units in the molecule Based on discovery.

According to the present invention, a paste is provided.

There is no restriction on the definition of the term paste. However, the paste can be applied through common application techniques, such as printing techniques (e.g., screen printing or stencil printing), dispersion techniques, spray techniques, pin transfer or dipping, Is understood to mean any dispersion having a viscosity and adherence sufficiently high so that the paste can be processed in a subsequent step.

The paste according to the present invention comprises (a) metal particles.

The metal particles are understood to mean particles which preferably contain metals.

According to one preferred embodiment, the metal is selected from the group consisting of copper, silver, nickel, and aluminum. According to a particularly preferred embodiment, the metal is silver.

The metal may be a pure metal, for example, as a pure metal having a purity of at least 99 wt%, a purity of at least 99.9 wt%, a purity of at least 99.99 wt%, or a purity of at least 99.999 wt%. On the other hand, the metal particles may also contain a plurality of metals. The metal particles may contain an alloy or intermetallic phase made of a plurality of metals.

According to one preferred embodiment, the metal particles comprise as elements the element selected from the group consisting of silver, copper, nickel and aluminum. In the scope of the present invention, it is understood that the main component means a component which exists in a larger fraction than any other component present in the target metal particle.

According to a particularly preferred embodiment, the metal particles are silver particles, copper particles, nickel particles or aluminum particles. The particles, if appropriate, may be partially or totally oxidized at their surface.

According to a particularly preferred embodiment, the metal particles are silver particles.

There is no restriction on the shape of the metal particles. Preferably, the metal particles may take the form of flakes, ellipses, or rounds. The metal particles may be a mixed form of plural shapes.

According to a particularly preferred embodiment, the metal particles have a flake shape. In this embodiment, the fraction of flakes is preferably at least 70 wt%, more preferably at least 80 wt%, even more preferably at least 90 wt%, particularly preferably at least 99 wt%, based on the total weight of the metal particles .

According to another preferred embodiment, the metal particles have a length ratio of more than 1.0, more preferably a length ratio of more than 1.2, even more preferably a length ratio of more than 1.5, particularly preferably a length ratio of more than 2.0. Preferably, the metal particles have a length ratio of 20 or less, more preferably a length ratio of 15 or less, and even more preferably a length ratio of 10 or less. In context, the length ratio is the distance (a) extending through the widest portion of the cross-section of the metal particle along a line perpendicular to the distance (a) b "). < / RTI > In this case, the cross section is a section across the metal particles having the largest surface area. If the metal particles have, for example, a rectangular cross section, the length ratio is the ratio of the length to the width of the cross section. For example, metal particles having a rectangular cross section with a length of 2 탆 and a width of 1 탆 have a length ratio of 2.

According to another preferred embodiment, the fraction of the metal particles whose length ratio exceeds 1.0, more preferably the fraction of metal particles whose length ratio exceeds 1.2, and even more preferably the fraction of metal particles whose length ratio exceeds 1.5, Is at least 70% by weight, more preferably at least 80% by weight, and even more preferably at least 90% by weight based on the total weight of the particles.

The metal particles present in the paste may have various particle size distributions.

According to one preferred embodiment, the average particle size (d50 value) of the metal particles is at least 500 nm, more preferably at least 650 nm, even more preferably at least 1 탆. The average particle size (d50 value) is preferably 20 占 퐉 or less, more preferably 15 占 퐉 or less, and still more preferably 10 占 퐉 or less. Therefore, the average particle size (d50 value) is preferably in the range of 500 nm to 20 占 퐉, more preferably in the range of 650 nm to 15 占 퐉, and still more preferably in the range of 1 to 10 占 퐉. Preferably, the average particle size (d50 value) is interpreted to mean a particle size not exceeding 50 vol% of the metal particles and a particle size exceeding 50 vol% of the metal particles.

According to another preferred embodiment, the particle size d10 (d10 value) of the metal particles is at least 150 nm, more preferably at least 200 nm, even more preferably at least 250 nm. The particle size d10 (d10 value) is preferably 5 mu m or less, more preferably 4 mu m or less, and still more preferably 3 mu m or less. Therefore, the particle size d10 (d10 value) is preferably in the range of 150 nm - 5 mu m, more preferably in the range of 200 nm - 4 mu m, and still more preferably in the range of 250 nm - 3 mu m. Preferably, the particle size d10 (d10 value) is interpreted to mean a particle size not exceeding 10 vol% of the metal particles and a particle size exceeding 90 vol% of the metal particles.

According to another preferred embodiment, the particle size d90 (d90 value) of the metal particles is 1.75 占 퐉 or more, more preferably 2 占 퐉 or more, even more preferably 2.25 占 퐉 or more. The particle size d90 (d90 value) is preferably 100 占 퐉 or less, more preferably 50 占 퐉 or less, and still more preferably 25 占 퐉 or less. Therefore, the particle size d90 (d90 value) is preferably in the range of 1.75 - 100 탆, more preferably in the range of 2 - 50 탆, still more preferably in the range of 2.25 - 25 탆. Preferably, the particle size d90 (d90 value) is interpreted to mean a particle size not exceeding 90% by volume of the metal particles and a particle size exceeding 10% by volume of the metal particles.

The description of the particle size is applied to the analysis of the particle size measurement through the LALLS ( Low Angle Laser Light Scattering ) method according to ISO 13320 (2009). Preferably, a Mastersizer 2000 (Malvern Instruments Ltd., Worcestershire, UK) is used as the measuring instrument in the text. Measurement and analysis are carried out under appropriate conditions (for example: standard: refractive index of 0.14, silver with absorption of 3.99; dispersion medium: ethanol with a refractive index of 1.36; course: 200 ml of ethanol) 0.5 g of powder was added and the resulting suspension was ultrasonicated for 5 minutes and then the aliquot of the suspension for the measurement was loaded on a Mastersizer 2000 Hydro Transfer to Accessory ; Optical model for analysis: Mie theory).

Preferably, the metal particles have a specific surface area of 1 to 5 m 2 / g, more preferably 1 to 4 m 2 / g, according to a BET ( Brunauer , Emett , Teller ) measurement method. Preferably, such BET measurements are performed in accordance with DIN ISO 9277: 2003-05.

If appropriate, the metal particles may also be present in a mixed form of a plurality of fractions of the metal particles. The fraction may vary, for example, in composition, shape or size of the metal particles.

Preferably, the fraction of metal particles is at least 50 wt%, more preferably at least 60 wt%, even more preferably at least 70 wt%, particularly preferably at least 80 wt%, based on the total weight of the paste. Preferably, the fraction of metal particles is at most 95% by weight, more preferably at most 93% by weight, even more preferably at most 90% by weight relative to the total weight of the paste. Accordingly, the fraction of the metal particles is [preferably] in the range of 50 to 95% by weight, more preferably in the range of 60 to 93% by weight, and still more preferably in the range of 70 to 90% by weight, based on the total weight of the paste.

The metal particles may comprise a coating.

In the scope of the present invention, the coating of the metal particles is interpreted to mean a solid adhesion layer on the surface of the metal particles. Preferably, the rigid adherent layer means a layer that is not easily detached from the metal particles under gravity.

The coating of metal particles generally contains at least one coating compound.

The at least one coating compound is preferably an organic compound.

Preferably, the coating compound is selected from the group consisting of a saturated compound, a mono-unsaturated compound, a multi-unsaturated compound, and mixtures thereof.

Preferably, the coating compound is selected from the group consisting of a branched chain compound, an unbranched chain compound, and mixtures thereof.

Preferably, the coating compound has 8 to 28, more preferably 12 to 24, particularly preferably 12 to 18 carbon atoms.

According to one preferred embodiment, the coating compound is selected from the group consisting of fatty acids, fatty acid salts, and fatty acid esters.

Fatty acid salts that may be considered are preferably fatty acid salts wherein the anionic component is a deprotonated fatty acid and the cationic component is selected from the group consisting of ammonium ion, monoalkylammonium ion, dialkylammonium ion, trialkylammonium ion, lithium ion, sodium ion, , And an aluminum ion.

Preferred fatty acid esters are derived from the corresponding fatty acids in which the hydroxyl group of the carboxylic acid unit has been replaced by an alkyl group, especially a methyl, ethyl, propyl or butyl group.

According to one preferred embodiment, the at least one coating compound is selected from the group consisting of caprylic acid (octanoic acid), capric acid (decanoic acid), lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid Hexadecanoic acid), stearic acid (octadecanoic acid), mixtures thereof, as well as the corresponding esters and salts, and mixtures thereof.

According to a particularly preferred embodiment, the at least one coating compound is selected from the group consisting of lauric acid (dodecanoic acid), stearic acid (octadecanoic acid), sodium stearate, potassium stearate, aluminum stearate, copper stearate, sodium palmitate, And potassium palmitate.

Coated metal particles which are preferably used are commercially available. Corresponding coating compounds may be applied to the surface of the metal particles through techniques common in the art.

For example, coating compounds, in particular the stearates or palmitates mentioned above, can be slurried in a solvent and the slurried coating compound can be triturated with the metal particles in a ball mill. After grinding, the metal particles coated with the coating compound are dried and then the dust is removed.

Preferably, the fraction of the at least one coating compound selected from the group consisting of fatty acids, fatty acid salts, and fatty acid esters is at least 80 wt%, more preferably at least 90 wt%, particularly preferably at least 95 wt% %, Even more preferably at least 99 wt%, especially at least 100 wt%.

According to one preferred embodiment, the total fraction of the coating compound is from 0.05 to 3% by weight, more preferably from 0.07 to 2.5% by weight, even more preferably from 0.1 to 2.2% by weight, based on the total weight of the coated metal particles.

The degree of coating defined as the mass of the coating compound: the ratio of the surface area of the metal particles is preferably from 0.00005 to 0.03 g, more preferably from 0.0001 to 0.02 g, per square meter (m 2) of the surface area of the metal particles, Is 0.0005-0.02 g of a coating compound.

Surprisingly, it has been found that having a coating on metal particles greatly improves reliability in the bond strength between the electronic device and the substrate.

According to the present invention, the paste also contains at least one activator (b).

The activator contains two or more carboxylic acid units in the molecule. Thus, the active agent may also contain more than 2, more than 3, or more than 4 carboxylic acid units in the molecule.

The position of the carboxylic acid unit in the molecule is not limited. However, the carboxylic acid unit of the active agent is preferably located at the terminal position.

In addition, the carboxylic acid unit of the activator may contain not more than 5 carbon atoms, more preferably not more than 4 carbon atoms, even more preferably not more than 3 carbon atoms, particularly preferably not more than 2 carbon atoms, Particularly preferably not more than one carbon atom. It is also preferred that the carboxylic acid units of the activator are connected to one another via one or more carbon atoms. When determining the number of carbon atoms to which the carboxylic acid units of the activator are connected, the carbon atoms of the carboxylic acid unit itself are not included in the calculation according to the scope of the present invention. Thus, for example, in the case of malonic acid (HOOCCH ₂ COOH), the carboxylic acid units are linked together through one carbon atom, while in the case of maleic acid (HOOC (CH ₂ COOH) They are interconnected via atoms.

According to one preferred embodiment, the activator comprises two or more carbon atoms, more preferably three or more carbon atoms. Preferably, the activator contains no more than 18 carbon atoms, more preferably no more than 14 carbon atoms, even more preferably no more than 12 carbon atoms, particularly preferably no more than 10 carbon atoms, Contains up to 8 carbon atoms, especially up to 6 carbon atoms. Thus, the activator preferably has 2 to 18 carbon atoms, more preferably 2 to 14 carbon atoms, even more preferably 2 to 12 carbon atoms, particularly preferably 2 to 10 carbon atoms, Contains 2 to 8 carbon atoms, especially 2 to 6 carbon atoms or 3 to 6 carbon atoms.

The activator may be a saturated or an unsaturated compound.

The unsaturated activator preferably comprises at least one carbon-carbon double bond in the molecule. It has also been found that cis-isomers are particularly advantageous activators.

The active agent may be a branched or non-branched chain compound.

There is no restriction on the length, type and position of the side chain of the branched chain activator. Preferably, the branched actives comprise at least one side chain having a length of from 1 to 8 carbon atoms. In general, the side chain is an alkyl chain, which may be substituted as appropriate.

The activator may be aromatic or aliphatic. However, the activator is preferably an aliphatic compound.

In addition to the oxygen atoms present in the carboxylic acid units, the active agents according to the invention may further comprise hetero atoms. However, the activator preferably does not contain any heteroatoms other than the oxygen atoms in the carboxylic acid unit.

Preferably, the carboxylic acid unit of the active agent is present in a nonprotonated form in the paste. Therefore, it may be advantageous to select a suitable dispersing medium to prevent dissociation of carboxylic acid units.

In many cases it has proven advantageous for the activator to have a decomposition point of less than 300 ° C, more preferably less than 270 ° C, even more preferably less than 240 ° C, particularly preferably less than 200 ° C . In this case, the decomposition point of the active agent is preferably in the range of from 100 to 300 ° C, more preferably from 110 to 270 ° C, even more preferably from 120 to 240 ° C, particularly preferably from 130 to 200 ° C.

It has also proven advantageous in many cases that the melting point of the activator is at least 80 ° C, more preferably at least 90 ° C, even more preferably at least 100 ° C. In this case, the melting point is preferably 200 ° C or lower, more preferably 180 ° C or lower, still more preferably 160 ° C or lower. Thus, preferably, the melting point of the active agent is in the range of 80-200 ° C, more preferably in the range of 90-180 ° C, even more preferably in the range of 100-160 ° C.

The active agent can be present in its non-complexed form. On the other hand, the activator may also be present in a complex form, preferably as a complex comprising a subgroup element of the Periodic Table of the Elements. If the active agent is present in complexed form, it may be a particularly complexed dicarboxylic acid.

According to one preferred embodiment, the active agent is selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, cis-butenedioic acid (maleic acid), trans-butenedioic acid (fumaric acid) Pentanoic acid, trans-2-pentenoic acid, and dimethylmalonic acid.

According to a particularly preferred embodiment, the active agent is selected from the group consisting of oxalic acid, malonic acid, maleic acid, and dimethyl malonic acid.

According to a more particularly preferred embodiment, the activator is selected from the group consisting of oxalic acid, malonic acid, maleic acid, and dimethyl malonic acid.

The fraction of the active agent is preferably at least 0.1% by weight, more preferably at least 0.3% by weight, even more preferably at least 0.5% by weight, particularly preferably at least 1% by weight, 2% by weight or more. Preferably, the fraction of active agent is at most 30% by weight, more preferably at most 20% by weight, even more preferably at most 10% by weight, particularly preferably at most 7% by weight, Is not more than 5% by weight. Accordingly, the fraction of the active agent is in the range of 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, still more preferably 0.5 to 10% by weight, particularly preferably 1 to 7% by weight, Even more preferably in the range of 2 - 5% by weight.

In addition, the paste according to the present invention contains the dispersion medium (c).

The metal particles (a) are preferably dispersible in the dispersion medium (c). More than one active agent (b) may also be dispersible in the dispersion medium (c). However, the active agent (b) may be soluble in the dispersion medium (c).

The dispersion medium may be a dispersion medium customary in the art.

Thus, the dispersion medium may contain one or more solvents.

For example, organic compounds are solvents that can be considered in this context.

The organic compound preferably contains 5 to 50 carbon atoms, more preferably 8 to 32 carbon atoms, even more preferably 18 to 32 carbon atoms.

The organic compound may be branched or unbranched. The organic compound may also be a cyclic compound.

The organic compounds may also be inherently aliphatic or aromatic.

In addition, the organic compound used as a solvent may be a saturated or mono-or multi-unsaturated compound.

The organic compound may also contain a heteroatom, especially an oxygen atom or a nitrogen atom. The heteroatom may be part of a functional group. The functional groups that may be considered include, for example, carboxylic acid groups, ester groups, keto groups, aldehyde groups, hydroxyl groups, amino groups, amide groups, azo groups, imide groups, cyano groups or nitrile groups.

Thus, for example, it is possible to use a compound of formula (I), such as alpha-terpineol ((R) - (+) - alpha-terpineol, (S) terpineol, mixtures of the above terpineols, N-methyl-2-pyrrolidone, ethylene glycol, dimethylacetamide, alcohols, especially non-branches with 5-9 carbon atoms 1-hexanol, 1-octanol, 1-dodecanol, 1-tridecanol, 2-tridecanol, 3-tridecanol, 4-tridecanol, 5-tridecanol (Preferably dimethyl ester of glutaric acid, adipic acid or succinic acid or a mixture thereof), glycerol, diethylene glycol, di (triethylene glycol), triethylene glycol, triethylene glycol, Ethylene glycol or a mixture thereof may be used as the solvent.

According to another preferred embodiment, the dispersion medium contains one or more aprotic solvents. The fraction of the at least one aprotic solvent is at least 70 wt%, more preferably at least 80 wt%, even more preferably at least 90 wt%, based on the total weight of all components of the paste that is liquid at a temperature of 25 캜 and a pressure of 1.1013 bar %, Particularly preferably not less than 95% by weight, still more preferably not less than 99% by weight.

The aprotic solvent is preferably selected from the group consisting of aliphatic hydrocarbon compounds, carboxylic acid esters, and ethers.

According to a particularly preferred embodiment, the dispersion medium contains at least one aliphatic hydrocarbon compound. The aliphatic hydrocarbon compound preferably contains 5 to 50 carbon atoms, more preferably 8 to 32 carbon atoms, even more preferably 18 to 32 carbon atoms.

Thus, the aliphatic hydrocarbon compound may also be paraffin.

The fraction of the dispersion medium is preferably at least 5% by weight, more preferably at least 8% by weight, and even more preferably at least 10% by weight based on the total weight of the paste. Preferably, the fraction of the dispersion medium is 40 wt% or less, more preferably 30 wt% or less, still more preferably 20 wt% or less, particularly preferably 15 wt% or less, based on the total weight of the paste. Accordingly, the fraction of the dispersing medium is preferably in the range of 5 to 40 wt%, more preferably 8 to 30 wt%, and still more preferably 10 to 20 wt% with respect to the total weight of the paste.

The paste according to the present invention may contain, in addition to the metal particles (a), the at least one activator (b), and the dispersion medium (c), if appropriate, additional substances.

Additional materials that may be considered are diluents, thickeners, and stabilizers that are common in the art.

Preferably, the fraction of materials excluding (a) metal particles, (b) at least one activator having at least two carboxylic acid units in the molecule, and (c) a dispersing medium is at most 20% More preferably not more than 15% by weight, even more preferably not more than 10% by weight, particularly preferably not more than 5% by weight, even more preferably not more than 3% by weight, especially not more than 1% by weight.

The paste according to the present invention can be produced by means common in the art.

The paste may be prepared, for example, by mixing (a) metal particles, (b) at least one activator having at least two carboxylic acid units in the molecule, and (c) a dispersing medium.

According to a particularly preferred embodiment, the paste is prepared in multiple stages.

In this context, one or more active agents (b) are milled in a first step. The milling can proceed in a mill and serves to improve the dispersibility of the active agent in the dispersion medium (c).

The active agent (b) pulverized in the second step can then be combined with the dispersion medium (c). At this stage, it is common to prepare a uniform suspension of the active agent (c) in the dispersion medium (c). To prepare the homogeneous suspension, the mixture may be treated with a mixer, such as an Ultraturax mixer where appropriate.

Finally, the suspension obtained in the second step can be combined with the metal particles (a) in the third step. The resulting mixture is then homogenized, for example, manually if appropriate. The mixture can then be further homogenized after repeated passes through the roller mill if necessary. The resulting paste can then be used for the intended application.

The paste according to the present invention is preferably used to connect one or more electronic elements to one or more substrates.

In the present method, one or more electronic elements are preferably fixed on the substrate.

The fixation is accomplished through sintering. In the scope of the present invention, sintering is interpreted to mean connecting two or more components through heating without forming a liquid phase. Thus, the sintering preferably provides a firmly connected connection between the one or more electronic elements and the substrate.

As is known in the art, electronic devices are interpreted to be objects that can be part of an electronic arrangement. According to a preferred embodiment, the electronic device is interpreted as meaning a single component that can no longer be disassembled and can function as a component of an electronic circuit. As a unit, the electronic device can be composed of a plurality of components as appropriate. The electronic device can be, for example, an active device or a passive device. According to certain embodiments, electronic devices are used in high power electronic devices. Preferably, the electronic device is selected from the group consisting of diodes (e.g. LEDs, light emitting diodes ), transistors (e.g. IGBTs, insulated-gate bipolar transistors , bipolar transistors with insulated gate electrodes), integrated circuits, bare) is selected from the group consisting of a chip (die), a resistor, a sensor, a capacitor, a coil, and a heat sink (heat sink).

In general, the substrate is interpreted to mean an object that can be connected to an electronic device. According to one preferred embodiment, the substrate is a lead frame , a DCB substrate ( direct-copper- bonded Substrate), and a ceramic substrate.

According to one preferred embodiment, the pair to the electronic component and the substrate are connected to each other: LED / lead frames, LED / ceramic substrate, the die / leadframe, a die / ceramic substrate, the die / DCB substrate, the diode / lead frame, the diode / a ceramic substrate, a diode / DCB substrate, IGBT / leadframe, IGBT / ceramic substrate, IGBT / DCB substrate, an integrated circuit / lead frame, an integrated circuit / ceramic substrate, an integrated circuit / DCB substrate, the sensor / lead frame, a sensor / ceramic substrate, , A heat sink (preferably a copper or aluminum heat sink) / a DCB, a heat sink (preferably a copper or aluminum heat sink) / a ceramic substrate, a heat sink / lead frame , a capacitor (preferably a tantalum capacitor, Under unenclosed conditions) / lead frame .

According to another preferred embodiment, a plurality of electronic elements can be connected to the substrate. It may also be desirable to arrange electronic components on opposite sides of the substrate.

However, both the electronic device and the substrate include one or more contact regions.

In the scope of the present invention, the contact area is understood to mean the area of the electronic element that the substrate contacts through the paste according to the present invention, or the area of the substrate where the electronic element contacts through the paste according to the present invention. Thus, the contact area of the electronic device preferably comprises a contact surface once covered by the substrate once the substrate is connected thereto. In addition, the contact area of the substrate preferably includes a contact surface once covered by the electronic component once the electronic component is connected thereto. Preferably, the contact area of the electronic device has a volume defined by a thickness of 50 nm with the contact surface of the contact area of the electronic device (defined through the width and length of the contact surface). In addition, the contact area of the substrate preferably has a volume determined by a thickness of 50 nm with the contact surface of the contact area of the substrate (defined through the width and length of the contact surface). The volume of the electronic device and the contact area of the substrate has a predetermined weight. The weight can be determined, for example, by removing the contact area through sputtering by Auger spectroscopy and then measuring the weight of the removed area.

The contact region may be an area applied to the electronic element or substrate. For example, in many cases, metallisation is applied to the surface of the electronic device to be connected. The metallization may in many cases take up a thickness in the range of 100-400 nm. This type of metallization, or its area, may represent the contact area according to the present invention.

On the other hand, the contact area may also be an integral component of the electronic device or an integral component of the substrate. For example, according to the present invention, a lead frame made of copper can be used as a substrate. Such a leadframe may have a thickness in the range of a few millimeters. In this case, one region of the lead frame that does not necessarily differ from other regions of the lead frame in terms of material or structure may represent the contact region according to the present invention.

At least one of the electronic device and the contact area of the substrate contains one or more non-noble metals.

According to one preferred embodiment, at least one of the contact regions of the electronic device and the substrate comprising a noble metal comprises (i) at least one element selected from copper, aluminum, zinc and nickel, (ii) copper, aluminum, And (iii) an intermetallic phase comprising at least one element selected from copper, aluminum, zinc and nickel.

The proportion of one or more non-noble metals, for example, a non-noble metal selected from the group consisting of copper, aluminum, zinc and nickel, is preferably at least 5 wt%, more preferably at least 7 wt% , More preferably at least 10 wt%, particularly preferably at least 15 wt%, even more preferably at least 50 wt%, especially at least 90 wt%.

Preferably, a non-noble metal, more preferably a non-noble metal selected from the group consisting of copper, aluminum, zinc and nickel, is the main component of the contact area. In the scope of the present invention, the principal component of the contact region is understood to mean a component present in the contact region at a higher fraction than any other component present in the contact region.

In the scope of the present invention, the contact region comprising a non-noble metal may also include other components, especially noble metals.

If the contact region containing the non-noble metal contains an alloy comprising at least one element selected from copper, aluminum, zinc and nickel, the alloy may be an alloy or tin, such as, for example, copper, nickel, zinc and general impurities, , And an alloy containing a general impurity as a main component.

In a first step of the method according to the invention, an electronic device is provided having a substrate having a first contact region and a second contact region, wherein at least one of the contact regions contains a non-precious metal.

Thus, the contact area of the substrate, or the contact area of the electronic device, or the contact area of the electronic device and the contact area of the substrate may contain a non-noble metal.

Semantically, the substrate comprises a first contact area and the electronic device comprises a second contact area. In addition, the substrate or electronic component may include additional contact areas, if appropriate Can be. For example, if a leadframe is used as a substrate, the leadframe generally includes a plurality of (adjacent) contact regions intended to form a subassembly connected to a plurality of electronic components.

In the next step of the process according to the invention, a paste according to the definition given above is provided.

Accordingly, the paste contains (a) metal particles, (b) at least one activator having at least two carboxylic acid units in the molecule, and (c) a dispersing medium.

The structure is created in a further step of the method according to the invention.

The structure contains at least a substrate, an electronic device, and a paste. In this context, the paste is positioned between the first contact area of the substrate and the second contact area of the electronic device. Thus, the first surface of the substrate is in contact with the second surface of the electronic device by the face.

The structure may be created, for example, by applying the paste to the contact surface of the first contact area of the substrate and placing the electronic component by the contact surface of the second contact area on the applied paste. In addition, the structure may also be created, for example, by applying a paste to the contact surface of the second contact area of the electronic device and placing the substrate by the contact surface of the first contact area on the applied paste. Application of the paste may preferably be performed by application techniques well known in the art, such as printing (e.g., screen printing or stencil printing), dispersion techniques, spray techniques, pin transfer or immersion.

The distance between the first surface of the substrate and the second surface of the electronic device (determined substantially by the thickness of the paste immediately after fabricating the structure) is preferably in the range of 20-200 microns, more preferably 50-100 microns Range.

Once the structure is manufactured, it can be dried if appropriate. Preferably, the structure is dried at a temperature in the range of 80 - 200 캜, more preferably in the range of 100 - 150 캜. The drying is preferably carried out for 2 to 20 minutes, more preferably for 5 to 10 minutes. If desired, drying may also be carried out, alternatively or additionally, preferably during the preparation of the structure under the conditions mentioned above, for example before placing the electronic component on a paste applied to the substrate, Or the like, before placing the substrate on the substrate.

In a further step of the method according to the invention, the substrate, the electronic element and the structure containing the paste are sintered.

During sintering, at least a portion of the contact region and the metal particles present in the paste are fired together. The remaining components present in the paste are generally removed from the paste during this process, if appropriate after chemical conversion, for example by evaporation. The sintering proceeds based on the diffusion process, in which the components present in the metal particles of the paste are diffused into the contact region and the components present in the contact region are diffused into the intervening space formed by the metal particles of the paste. Due to the prevailing temperature and diffusion rate during this process, a stable and firmly coupled connection is formed.

Preferably, the sintering of the structure is carried out by heating at a temperature of at least 150 ° C, more preferably at least 175 ° C, even more preferably at least 200 ° C. Preferably, the sintering of the structure is carried out by heating at a temperature of 350 DEG C or less, more preferably 300 DEG C or less. Thus, the structure preferably has a temperature in the range of 150-350 ° C, more preferably in the range of 150-300 ° C, even more preferably in the range of 175-300 ° C, particularly preferably in the range of 200-300 ° C Lt; / RTI >

The heating is preferably carried out without applying any process pressure, i. E. At a process pressure of 0 kbar, but can be performed at an elevated process pressure, for example a process pressure of 1 kbar or more.

The heating is preferably carried out for 1 to 60 minutes, more preferably for 2 to 45 minutes.

There is no restriction on the atmosphere in which the heating is performed. However, preferably heating is carried out in an atmosphere containing oxygen.

The sintering is carried out in a suitable sintering apparatus known in the art and preferably capable of setting the aforementioned process parameters.

After sintering, a module is obtained which comprises at least a substrate and electronic components interconnected through a sintered paste.

According to a particularly preferred embodiment, the method according to the invention for connecting one or more electronic elements to one or more substrates is carried out through a contact area, wherein at least one of the contact areas contains copper as a non-precious metal. In this case it has proved to be particularly advantageous to use a paste containing (a) metal particles, (b) at least one compound selected from the group consisting of malonic acid, maleic acid, and oxalic acid as the active agent, and (c)

According to a further particularly preferred embodiment, a method according to the invention for connecting one or more electronic elements to one or more substrates is carried out through a contact area, wherein at least one of the contact areas contains nickel as a non-precious metal. In this case it has proved to be particularly advantageous to use a paste containing (a) metal particles, (b) at least one compound selected from the group consisting of dimethyl malonic acid and oxalic acid as the activator, and (c) a dispersion medium.

The present invention will be described based on the following examples, which do not limit the scope of the present invention.

Example :

Paste 1 - 3 and Reference Paste 1 - 3 according to the present invention were prepared as follows in the composition according to the following Table 1:

Composition of Paste 1 - 3 and Reference Paste 1 - 3 Paste 1 Paste 2 Paste 3 Reference paste 1 Reference paste 2 Reference paste 3 Silver particles 85 wt% 85 wt% 85 wt% 85 wt% 85 wt% 85 wt% paraffin 12 wt% 12 wt% 12 wt% 12 wt% 12 wt% 12 wt% Activator: Malonic acid 3 wt% - - - - - Maleic acid - 3 wt% - - - - Dimethyl malonic acid - - 3 wt% - - - silver Lactate - - - 3 wt% - - Propionic acid - - - - 3 wt% - Urea - - - - - 3 wt%

In six different samples (Paste 1 - 3 and Reference Paste 1 - 3), the corresponding activator in the coffee grinder was first finely ground and then added to the dispersion medium. A uniform suspension was prepared from the mixture using an Ultraturax mixer. The uniform suspension was then added to the silver powder. The resulting mixture was first homogenized manually using a spatula and then homogenized again by passing it three times through a roller mill to obtain Paste 1 - 3 and Reference Paste 1 - 3.

Paste 1 - 3 and reference paste 1 - 3 were used to connect the leadframe to the semiconductor chip.

For this purpose, a lead frame made of copper or nickel and a silver-coated semiconductor chip were used.

Paste 1 - 3 and Reference Paste 1 - 3 were applied to the corresponding lead frame of six samples. Then, the semiconductor chips were placed on the coated paste. The distance between the lead frame and the opposing surface of the semiconductor chip was 80 mu m. The thus obtained structure was preliminarily dried at a temperature of 150 DEG C for 5 minutes. Thereafter, the obtained structure was sintered at a temperature of 250 캜 without pressure.

After the sintering process, analysis was performed to evaluate the connection state between the semiconductor chip and the lead frame and the reliability of the connection.

The results for this analysis are summarized in Table 2.

Test results using Paste 1 - 3 and Reference Paste 1 - 3 contact  Non-precious metals in the zone Connection between semiconductor chip and lead frame Reliability of connection Paste 1 Copper Reliable connection Very good Paste 2 Copper Reliable connection Very good Paste 3 nickel Reliable connection Very good Reference paste 1 Copper No connection, semiconductor chip not attached to lead frame - Reference paste 2 Copper No connection, semiconductor chip not attached to lead frame - Reference paste 3 nickel No connection, semiconductor chip not attached to lead frame -

These tests show that only stable paste is formed when using paste 1-3 according to the present invention and not when reference paste 1-3 is used.

Claims (10)

(a) metal particles;
(b) at least one activator having at least two carboxylic acid units in the molecule; And
(c) dispersion medium
Paste containing. The paste according to claim 1, wherein the metal particles are silver particles. 3. The paste according to claim 1 or 2, wherein the active agent has a decomposition point in the range of 100-300 < 0 > C. The paste according to any one of claims 1 to 3, wherein the active agent is selected from the group consisting of dicarboxylic acids and complexed dicarboxylic acids. The paste according to any one of claims 1 to 4, wherein the active agent is selected from the group consisting of malonic acid, maleic acid, dimethylmalonic acid and oxalic acid. The paste according to any one of claims 1 to 5, wherein the dispersion medium contains an aliphatic hydrocarbon compound. A method of connecting one or more electronic devices to a substrate via a contact region, the at least one contact region containing a non-noble metal,
(i) providing an electronic device having a substrate having a first contact region and a second contact region, wherein at least one of the contact regions contains a non-noble metal;
(ii) (a) a metal particle;
(b) at least one activator having at least two carboxylic acid units in the molecule; And
(c) a dispersing medium;
≪ / RTI >
(iii) creating a structure through which the first contact area of the substrate contacts the second contact area of the electronic device through the paste; And
(iv) sintering the structure to produce a module comprising at least a substrate and an electronic component interconnected via a sintered paste. 8. The method of claim 7, wherein at least one of the contact regions is an integral component of an electronic component or an integral component of a substrate. 9. The process according to claim 7 or 8, wherein the non-noble metal is copper and the activator is selected from the group consisting of malonic acid, maleic acid and oxalic acid. 9. The process according to claim 7 or 8, wherein the noble metal is nickel and the activator is selected from the group consisting of dimethyl malonic acid and oxalic acid.